The present invention relates in general to an integrated engine cooling and cabin heating system for transportation vehicles, and, more specifically, to a method and apparatus for circulating coolant.
Historically, transportation vehicles powered by combustion engines have produced sufficient waste heat from the combustion to supply all the needed heat for warming the passenger cabin during cold weather. Considering regulations and marketplace demand for higher fuel economy and lower emissions, the global automotive market is rapidly evolving to require alternative fuel vehicles and higher efficiency (lower waste heat) engines. Modern energy-efficient vehicles such as battery electric, hybrid, fuel cell, diesel engine, small displacement petrol engine vehicles pose challenges for cabin heating. In many cases an auxiliary heating device such as fuel-operated heater, a positive temperature coefficient (PTC) coolant heater, or an exhaust heat recovery system is utilized to raise the temperature of the coolant fluid that flows to the cabin heat exchanger (i.e., heater core). Plug-in hybrid vehicles in particular require an auxiliary heating device since the combustion engine is off and cannot generate heat during times that vehicle propulsion is provided by the battery-powered systems.
To provide warmed coolant to a cabin heat exchanger under all operating modes of the vehicle propulsion or powertrain system, a reconfigurable coolant loop is known that uses electronically-controlled valves to either bypass or include the combustion engine or other components in the active coolant flow depending on whether they are active. In one example of a cooling system architecture, coolant flow can be configured as either two (dual) loops for auxiliary-based cabin heating or one combined loop for engine-based heating. The first loop may include the primary energy source (power plant), a primary coolant pump, and other primary heat exchange devices (e.g., radiator or other heat sinks, deaeration device, oil coolers/heaters, EGR cooler, or turbocharger intercooler). The second loop may include the auxiliary heating device, cabin heat exchanger, and an auxiliary coolant pump. This dual loop configuration allows the auxiliary heating device to provide cabin heating using less energy and more quickly since a smaller mass of coolant is being pumped and heated and since none of its heat is lost to the primary power plant or its associated devices.
Conventional systems have required expensive electrical diverter valve(s), mounting brackets, fasteners, wiring, connectors, fusing, electronic controller, and/or software development in order to satisfy the functions of determining which mode to operate the coolant circuit and actually diverting the flow as required. It would be desirable to provide more cost effective solutions for the control and diversion of the coolant flow.